Bt transgenes minimally influence maize grain yield and lodging across plant populations

Adoption of maize (Zea mays L) hybrids containing Bt (Bacillus thuringiensis) transgenes and increased plant population is widespread but little scientific research exists on their interactions with production environments in the Western Maize Belt of the United States. Two pairs of near-isogenic Bt and non-Bt maize hybrids were grown under rainfed and irrigated conditions from 2008 to 2010 at target populations from 49,300 to 111,100 plants ha-1 near Mead, NE. The objective was to determine the influence of the presence/absence of Bt transgenes for European corn borer [Ostrinia nubilalis (Hübner) - ECB] and corn rootworm [Diabrotica spp. - CRW] on maize yield and lodging across a range of target populations. Bt maize hybrids produced 0.6 Mg ha-1 more grain, 0.2 more ears m-2, and 1.3 g heavier 100-kernel weight than non-Bt hybrids in absence of visible ECB and CRW rootworm pressure. Yield of Bt and non-Bt hybrids responded similarly to increasing target population, with Dekalb DKC 58-16 and 58-19 increasing from 11.0 to 13.1 Mg ha-1 and Dekalb DKC 61-69 and 61-72 from 11.8 to 12.7 Mg ha-1 as the target population increased from 49,300 to 111,100 plants ha-1. Lodging increased linearly with increasing target population, with a greater increase in rainfed than irrigated environments. Lodging of Bt and non-Bt maize hybrids was inconsistent. Grain yield, seed and insecticide cost, likelihood of ECB and CRW infestation, and environmental concerns related to soil insecticide use should be the drivers when determining if Bt maize hybrid use is justified. If CRW resistance occurs, planting non-Bt maize hybrids along with application of soil insecticide is a viable alternative.